In recent years, time-of-flight (ToF) cameras have emerged as a popular 3D imaging technology in several scientific and consumer applications, such as robot navigation, motion capture, human computer interfaces, and 3D mapping. Impulse ToF (sometimes referred to as direct ToF) systems estimate scene depths by emitting a short light pulse into the scene, and directly measuring the travel time of the reflected pulse. For example, impulse ToF techniques were used in LIDAR systems designed nearly 50 years ago, and several current commercial range estimation systems are based on impulse ToF techniques as well. While these systems are conceptually simple, they often require expensive components (e.g., high-speed sensors) and large bandwidth. Consequently, impulse ToF systems may not be practical for many consumer applications. Continuous-wave ToF (C-ToF) imaging systems (sometimes referred to as indirect ToF), which usually include temporally modulated light sources and image sensors, typically only require low-cost and low-power components, do not require a large baseline for measuring depth, and thus, can potentially measure accurate 3D shape over a large range of standoff distances. These properties have made C-ToF systems preferred for many low cost and/or consumer applications.
One limitation of current C-ToF camera systems, however, is limited depth resolution, especially in low signal-to-noise ratio (SNR) scenarios. Although the spatial resolution of these systems continues to rise with advances in image sensor technology, the depth resolution is fundamentally limited by noise, such as photon noise. One way to increase the SNR is to use a more powerful light source or to increase the capture time. However, this is not always possible as most devices, especially in consumer and outdoor settings, often operate on a tight power and time budget.
With the increasing popularity of these systems, efforts have been made to improve the accuracy that can be achieved with existing coding systems (e.g., sinusoid based modulation and/or demodulation). For example, techniques for mitigating depth errors in sinusoid coding based systems when the modulation functions are not perfectly sinusoid (e.g., due to the presence of higher order harmonics) have been explored. In parallel, techniques based on a few other specific modulation functions have been proposed, such as square functions, triangular functions, ramp functions, and pseudo random binary sequences. However, while these techniques and coding functions may incrementally improve the precision that can be achieved using C-ToF imaging systems, coding schemes that offer more precision are desirable.
Accordingly, new systems, methods, and media for encoding and decoding signals used in time-of-flight imaging are desirable.